Quiz 4

Question 1

Fischer projections

Answer 1

used to draw complex molecules (usually sugars) with multiple chiral centers

Question 2

are the horizontal lines on a fichser projection dashed or wedged?

Answer 2

horizontal lines are wedged/ coming out of page

Question 3

Are vertical lines on a Fischer projection dashed or wedged?

Answer 3

dashed/ going into the page

Question 4

why does the reaction happen? are products more stable than reactants?

Answer 4

thermodynamics

Question 5

how does the reaction happen? how do temperature and concentration affect the rate of reaction? How fast does the reaction happen?

Answer 5

Kinetics

Question 6

enthalpy (H)

Answer 6

the exchange of energy between a system and its surroundings for any process

Question 7

to calculate heat of reaction its — minus —

Answer 7

reactants minus products

Question 8

True or false?

Most reactions will require the breaking and forming of bonds

Answer 8

True, think about all the reaction mechanisms you will learn

Question 9

Entropy (S)

Answer 9

The measure of disorder within a system

using probablity and liklihood

Question 10

What sign of enthalpy is favorable and nonfavorable

Answer 10

posititve enthalpy (endothermic)= non favorbale
negative enthalpy (exothermic)= favorbale

Question 11

What sign of entropy is favorable and non favorbale?

Answer 11

positive entropy = favorable
negative entropy = non favorable

needs to be positive so G can be negative

Question 12

What sign of G indicates a spontaneous reaction?

Answer 12

negative g

positive g is non spon

Question 13

negative G, where products are lower energy than reactants, spontaneous

Answer 13

exergonic

Question 14

positive g, where products are higher energy than reactions, non spon

Answer 14

endergonic

like how endothermic is not favorbale, neither is endergonic

Question 15

Keq> 1

Answer 15

products are favored, reaction proceeds towards products

Question 16

Keq<1

Answer 16

reactants are favored, reaction proceeds towards reactants

Question 17

Keq = 1

Answer 17

rxn is at equilibrium

Question 18

True or false?

Spontanenous does not mean slow!

Answer 18

false, spontaneous does not mean fast!

but ig it also doesnt mean the first thing

Question 19

Name the four factors that can affect the rate constant

Answer 19

1. Energy of activation
2. Temperature
3. Steric/ geometric orientation
4. presence of a catalyst

Question 20

True or false?

A catalyst can speed up a reaction by lowering the Ea by changing transition state orientation?

Answer 20

false! a catalyst can never lower the energy of activation

Question 21

transition state

Answer 21

the peaks of an energy diagram, where bonds are actively being broken and formed, unstable/high energy

Question 22

What can a transition state tell you about the number of mechanistic steps of a reaction?

Answer 22

the number of tranisition states on the graph show the number of mechanistic steps

Question 23

Intermediates

Answer 23

certain, but short lifespan, appear on the wells of the graph, more stable/lower energy

Question 24

Activation energy

Answer 24

the amount of energy it takes to complete a reaction, the more it takes the slower the reaction

Question 25

Hammonds Postulate

Answer 25

- in exergonic reactions, the transition states are closer in energy to the reactants so they will structurally be more similar to the reactants - in endergonic reactions, the transition states are closer in energy to the products so they will structurally be more similar to the products

Question 26

Nucleophile

Answer 26

electron dense wants to give up electrons - often negatively charged or w/ a l.p. - double bonds (electron dense) - lewis base

Question 27

examples of nucleophiles

Answer 27

1. halides (NOT ALKYL HALIDES) 2. bases 3. alcohols 4. water (weak nucleophile)

Question 28

electrophiles

Answer 28

e-deficient, accepts lone pairs - often a positive charge - lewis acid

Question 29

examples of electrophiles

Answer 29

1. alkyl halides 2. carbonyl groups 3. carbocations

Question 30

Arrows starts at a place of electron --- and points to a place of electron ---

Answer 30

density, deficiency

Question 31

nucleophilic attack

Answer 31

nucleophile attacks and attatches to electrophile - arrow from negative charge to positive charge

Question 32

Loss of a leaving group

Answer 32

grp skedaddles off of molecule (often a terminal halogen) - one atom takes both e-

Question 33

Proton transfer | acid/base

Answer 33

two arrows, proton leaves one atom and moves to another

Question 34

carbocation re-arrangement

Answer 34

stabilizing a carbocation by moving a methyl or hydride grp to fill empty p orbital w/ electrons

Question 35

# True or false? Nucleophilic attack should be drawn in before a carbocation re-arrangement?

Answer 35

False, a carbocation ion will stabilize with re-arragnment before attack if it can

Question 36

# True or false? methyl and hydride shifts can occur with any methyl or hydride grp on a molecule?

Answer 36

false, it can only be adjacent methyls or hydrides

Question 37

Steps to determining if a re-arrangement is right

Answer 37

1. Identify all adjacent carbons to the carbocation 2. Identify all adjacent methyl and hydride groups 3. draw out methyl and hydride shift to see if either create a more stable carbocation

Question 38

substitution reactions

Answer 38

nucleophile replaces alkyl halide on the molecule | nucleophilic attack + loss.of leaving grp

Question 39

elimination reactions

Answer 39

reagents act as a base for a proton transfer and formation of pi bond | proton transfer + loss of leaving grp

Question 40

# true or false? Substitution and elimination reactions only occur at Sp3 hybridized carbon atoms.

Answer 40

True, sp2 has too high of activation barrier

Question 41

What are two reasons halogens promote substitution and elimination reactions?

Answer 41

1. Halogens draw e-density away by induction creating a e- deficient place for nucleophilic attack 2. alkyl halides make good leaving groups

Question 42

alpha carbon

Answer 42

carbon directly attatched to alkyl halide

Question 43

beta carbon

Answer 43

carbon adjacent to alkyl halide

Question 44

Is the subsitution rxn more sensitive to substituents on the alpha or beta carbon

Answer 44

alpha carbon, but still senstive on beta carbon just not as much

Question 45

at what amnt of substituents attatched to the alpha or beta carbon will the reaction no longer happen?

Answer 45

on a tertiaty alpha or beta carbon

Question 46

Steric Hindrence

Answer 46

crowding of the alpha carbon by groups that are not H groups

Question 47

concerted rxn

Answer 47

all mechanistic steps happen at one, one intermediate

Question 48

stepwise reaction

Answer 48

more than one mechanistic step, more than one transition state